The present invention relates to a heat exchanger which is suitably used as an evaporator of a car air conditioner, which is a refrigeration cycle to be mounted on an automobile, for example.
The present applicant has proposed a heat exchanger which is used as an evaporator of a car air conditioner and which satisfies the requirements for reduction in size and weight and higher performance (refer to Japanese Patent Application Laid-Open (kokai) No. 2003-75024). The heat exchanger includes first and second header tanks disposed apart from each other, and a heat exchange core section provided between the header tanks. In the first header tank, a refrigerant inlet header section having a refrigerant inlet and a refrigerant outlet header section having a refrigerant outlet are juxtaposed in an air flow direction. In the second header tank, a first intermediate header section and a second intermediate header section are juxtaposed in the air flow direction. The first intermediate header section and the second intermediate header section communicate with each other. The heat exchange core section includes a first heat exchange tube row, a second heat exchange tube row, and corrugate fins. The first heat exchange tube row includes a plurality of heat exchange tubes which are separated from one another in the longitudinal direction of the header tanks and whose opposite end portions are connected to the refrigerant inlet header section and the first intermediate header section, respectively. The second heat exchange tube row includes a plurality of heat exchange tubes which are separated from one another in the longitudinal direction of the header tanks and whose opposite end portions are connected to the refrigerant outlet header section and the second intermediate header section, respectively. The corrugate fins are disposed in air-passing clearances, each formed between heat exchange tubes adjacent to each other with respect to the longitudinal direction of the header tanks, and on the outer sides of the heat exchange tubes located at the opposite ends, in such a manner that the corrugate fins are shared by the heat exchange tubes of the first heat exchange tube row and those of the second heat exchange tube row. The corrugate fins are brazed to the heat exchange tubes of the first and second heat exchange tube rows.
In the heat exchanger disclosed in Japanese Patent Application Laid-Open No. 2003-75024, the refrigerant inlet of the refrigerant inlet header section and the refrigerant outlet of the refrigerant outlet header section are formed at the same end portion of the first header tank or in a longitudinal center portion of the first header tank at positions close to each other with respect to the longitudinal direction.
However, through various studies, the present inventor has found that, although the heat exchanger disclosed in Japanese Patent Application Laid-Open No. 2003-75024 usually has a sufficiently high heat exchange performance, when a further improvement of heat exchange performance is required, in some cases the heat exchanger fails to satisfy that requirement. That is, in the case where the refrigerant inlet of the refrigerant inlet header section and the refrigerant outlet of the refrigerant outlet header section are formed at the same end portion of the first header tank or in a longitudinal center portion of the first header tank at positions close to each other with respect to the longitudinal direction, when refrigerant flows from the refrigerant inlet to the refrigerant outlet, a large amount of the refrigerant may flow through heat exchange tubes of the first and second heat exchange tube rows, the heat exchange tubes being located close to the refrigerant inlet and the refrigerant outlet, and the amount of refrigerant flowing through the remaining exchange tubes may decrease, whereby the refrigerant flowing amounts of all the heat exchange tubes become non-uniform. As a result, the temperature of air having passed through the heat exchange core section becomes non-uniform; i.e., varies with location. Thus, the effect of further improving the heat exchange performance of the heat exchanger cannot be attained sufficiently.
In order to solve such a problem, the present applicant has proposed an improvement on the heat exchanger disclosed in Japanese Patent Application Laid-Open No. 2003-75024 (refer to, Japanese Patent Application Laid-Open (kokai) No. 2006-170598). In the improvement, the interior of the refrigerant inlet header section of the first header tank is partitioned into two spaces in the longitudinal direction of the heat exchange tubes by a first diverging flow control wall having a plurality of refrigerant passage holes; the interior of the refrigerant outlet header section of the first header tank is partitioned into two spaces in the longitudinal direction of the heat exchange tubes by a second diverging flow control wall having a plurality of refrigerant passage holes; the interior of the second intermediate header section of the second header tank is partitioned into two spaces in the longitudinal direction of the heat exchange tubes by a third diverging flow control wall having a plurality of refrigerant passage holes; and the interior of the first intermediate header section of the second header tank and the outer section of the second intermediate header section with respect to the longitudinal direction of the heat exchange tubes are connected together at one end portion of the second header tank.
According to the heat exchanger disclosed in Japanese Patent Application Laid-Open No. 2006-170598, diverging flow into all the heat exchange tubes of the two heat exchange tube row occurs uniformly, and the refrigerant flowing amounts of all the heat exchange tubes are rendered uniform, whereby heat exchange performance is improved further.
However, in the case of the heat exchanger disclosed in Japanese Patent Application Laid-Open No. 2006-170598, a large flow passage resistance acts on refrigerant when the refrigerant passes through the refrigerant passage holes of the first through third diverging flow control walls, whereby the heat exchange performance improving effect may be impeded.